Frequency divider



Nov. 18, 1958 P. J. DE VITA FREQUENCY mvrmaav Filed sept. 5, A195e NVNOhmlT United States Patent FREQUENCY DIVIDER Philip Joseph De Vita,Chicago, Ill., assignor to Hammond Organ Company, ChicagoIll., acorporation of Delaware Application September 5, 1956, Serial No.608,118 3 Claims. (Cl. Z50-36) 'cold cathode gas tubes together withinput pulse amplifying triodes, and employing a single source of platecurrent supply. When the input frequency does not vary appreciably, theoutput signals of the several stages may be either or both waves of thesubstantially sine or square type, to facilitate the use of thefrequency divider as a tone signal generator of an electrical musicalinstrument.

A further object is to provide an aperiodic frequency divider capable ofembodiment in any desired number of cascaded stages, in which thecomponents are relatively fewand in which the circuitry is relativelysimple.

A further object is to provide a multi-stage aperiodic frequency dividerwhich is stable and reliable in operation, despite variations of thefrequency and amplitude f of the input pulses and despite variations inthe'anode rA voltages.

Other objects will become apparent from the following description,reference being had to the accompanying' drawing which is a schematicwiring and block diagram of a frequency divider comprising seven stages.

The frequency divider comprises pulse input terminals 20 and 21, thelatter terminal being shown as connected to a common ground. Theterminal 20 is coupled to the grid 22 of a triode V-1A through acapacitor C26. A grid return resistor R28 connects the grid 22 to tap 35of a grid bias source comprising an adjustable tap resistor R30 `andfixed resistor R32 connected in series between ground and a terminal 100v. The adjustable tap resistor R30 has a bypass capacitor C34 connectedin parallel therewith, and the junction between resistors R30 and R32 isconnected to the cathode 36of the triode V-1A as well as to the eathodesof the corresponding triodes V1B to V-4A utilized in the succeedingstages. It will be noted also that the grid bias Voltage of all thetriodes V-1B to V-4A is determined by the adjustment of tap 35 ofresistor R30. The triodes are preferably twin triodes of the 12AX7 type.

Each stage of the divider includes a cold cathode gas tube 40 which hasan anode 6 connected by resistor R42 to a conductor 44 leading to a-l-370 v. terminal of the power supply, and each of these tubes has aguide electrode 2 connected by conductor 46 with the plate 48 of thetriode such as V-1A. A cathode electrode 1 in the tube 40 is connectedto the common ground through a resistor R50 in parallel with a capacitorC51, which are connected in series with a parallel network comprising aninductance L52 and capacitor C54. The inductance L52 forms the primaryof a transformer, the secondary L56 of which is connected between groundand an output terminal f/ZF. When the parallel network comprisinginductance L52 and capacitor C54 is adjusted to be resonant at thefrequency of pulses appearing on both cath- `next stage.

Patented Nov. 18, 1958 odes 1 and 3 of tube 40, the signal on terminalf/ZF with respect to ground, will be generally of sine wave shape, andin musical terms may be considered as resembling a ute-like tone. Thecathode electrode 3 of tube 40 is connected to a terminal f/2C, uponwhich the signal will appear as a substantially square wave,representative in musical terms as a tone resembling that of thewoodwind or clarinet family.

A cathode electrode 3 in the gas tube 40 is also connected to groundthrough resistor R60 which has a capacitor C62 connected in paralleltherewith. The conductor 46 is connected to ground through a resistorR62 and in addition is connected to the gaseous tube anode currentsupply conductor 44 by a resistor R64. These two resistors constitute avoltage divider to provide a voltage of approximately +37 v. on theguide electrode 2 in the absence of a triggering pulse.

The electrode 3 is connected through a capacitor C66 (which 'correspondsto the capacitor C26 of the first stage) to the control grid 67 of thetube V-IB of the similar to the rst stage described in detail, andsimilar reference characters have been applied to corresponding v parts,it being understood that there may be differences in particular valuesof the components in the successive stages to facilitate operation atthe different frequencies,

but most of the corresponding resistors willbe of the i same Value ineach of the stages.

The output terminals of the several stages are designated as fractionsof the input frequency f, followed by the letter R indicating flute, orthe letter. C, indicating clarinet.

In operation, an input frequency is impressed kacross the terminalsv 20,21, this input frequency being preferably in the form of positivepulses. If in the form 'of both positive and negative pulses, or otherpositive and negative wave form, only the positive portions will beeffective to trigger the triode V-lA.

Assuming that in the initial state, there is an-ionized y path betweenelectrodes 6 and 3 of tube 40, a positive pulse on the grid 22 of triodeV-1A will cause the anode 48 which is normally at a positive potentialwith respect to ground to go negative-possibility more negative than theground potential-and as a result there will be greater K potentialdifference between the anode 6 and guide electrode 2 than existedbetween the anode 6 and cathode electrode 3. which appears to the eye asla glow, willshift from the cathode electrode 3 to the guide electrode2.

When the anode 48 is returned to its normal potential, determined by thevoltage divider comprising R62.-

and R64 (R64 being approximately ten times as high in Value as R62 sothat the voltage on conductor 46 is approximately one-tenth theB-jvoltage of 370, namely, 3 about +37 v.), the fact that cathodeelectrode 1 is at somewhat lower potential causes the ionization toshift from guide electrode 2 to cathode electrode 1, and the tubecontinues to operate in this condition until a second positive pulseYsignal is supplied on the inputterminals 20, 21. Upon the secondimpulse, the ow pathl i' shifts from the cathode electrode 1 to theguide electrode 2 temporarily, and thereafter, upon cessation of thepulse impulse, the flow path shifts to cathode electrode 3. This isbecause the cathode electrode 1 was maintained at a higher potential dueto the charge temporarily retained in capacitor C51, whereas at the sametime the cathode electrode 3 will have been reduced to ground potentialdue to the discharge of capacitor C62 through resistor R60.

Upon reception of a third input pulse, the operation will be repeated,so that the two cathodes and the guide transfer current between anode 6in the order of elec- This stage and the succeeding stages are Thus, theionized path of current flow, f

3 trodes 3, 2, 1, 2, 3, 2, 1, etc., with the result that the inputfrequency is divided by a factor of 2 with respectl to the frequency ofthe pulses present on either electrodes 2 or 3.

The signal appearing on the cathode` electrode A3` is differentiated byvirtuev of the capacitor C66 and the resistancel R28 associated withthe-tube V-1B so that the signal for triggering the next stage is in theformof spikes with alternate positive and negative peaks, which isdesirable for accurate, stable operation of the second stage:

It is desirable for best results to keep the potential of guideelectrode 2 and anode 48 at a value above ground potential so that theguide electrode 2 will fire substantially near the peak of the negativepulse potential appearing on the anode 43. In other words, the guideelectrode 2 of gaseous tube 40 is fired to shift the ionic current pathand the current flow from either electrode 1 or electrode 3substantially near this negative peak rather than at the initiation ofor shortly following the initiation of the negative pulse on anode 48,which, if it occurred at the broader base portion of the negative pulsewould of course result in signal wave shape which would be less like theideal square wave shape desired at the signal output terminal f/ZC.

In view also of the fact that the guide electrode 2 and anode 48 arenormally maintained at a voltage above ground potential, variations inthe amplitude of input pulses and variations in the anode current supplyvoltage are less subject to influence the operation of the circuit,because, as the voltage on the conductor 44 drops, there is acorresponding drop in the positive bias potential on thefguide electrode2, and thus the amplitude of the negative pulse required to transfer thecurrent path to the guide electrode 2 of tube 40 may be ofcorrespondingly lower value.

In the particular exemplary form of the invention, there are sevenstages of frequency dividers so that, for example, if the apparatus isto be used in a musical tone generating system the input frequencyimpressed across the terminals 20, 21 may be 14,080 C. P. S. This inputfrequency may be derived from a suitable oscillator, the output of whichmay also be used to supply a tone frequency signal. Then the successivestages of the frequency divider apparatus will provide frequencies of7040, 3520, 1760, 880, 440, and 220, which are musically useful. Inanother way in which the invention may be utilized, the input frequencywill be provided by a variable frequency oscillator which may be tunedin any suitable manner to high harmonics of the semitones of 'a musicalscale. Such instrument in which this arrangement would be employed wouldbe of the melody type, and suitable switching means would be providedwhich would determine the particular stage or stages from which theoutput signal or signals would be derived. Such switching means are wellknown in the art.

In other forms in which the invention may be utilized, twelve frequencydividers and their corresponding driving oscillators, such as the oneshown in this application,

would be employed respectively tuned to provide the 50 twelve semitoneintervals for each of the five or six octaves in the register of anorgan type instrument. In either form of utilization of the invention,the custom- 4 ary filter, formant, octave coupler, and control circuits,as desired, may be used.

The apparatus of the invention may produce either or both output signalsof the substantially sine or square wave type which, in accordance withthe known methods, may be modified to produce a large variety of tonequalities.

Iclaim:

1. In a frequency divider for dividing successively by the factor oftwo, the combination of a plurality of similar cascaded stages, eachstage comprising a gaseous cold cathode tube having an anode, a pair ofcathodes, and a guide electrode; an input signal amplifier having ananode the potential of which drops when a positive input pulse issupplied to the amplifier; a connection between the anode of theamplifier and the guide electrode; common means for supplying operatingpotentials to the anode of the cold cathode gaseous tube and the anodeof the amplifier; meshes each comprising a capacitor in parallel with anon-capacitative impedance connected respectively between the gas tubecathodes and a point of fixed potential; means coupled to one of the gastube cathodes to derive an output signal therefrom; means coupled to theother of the gas tube cathodes to supply a triggering signal to theamplifier of the next stage, in which there is included a transformer inthe means coupled to one of the gas tube cathodes to derive an outputsignal therefrom, the transformer having primary and secondary windings;in which the mesh connected between one of the gas tube triodes and thepoint of fixed potential has as its non-capacitative impedance theprimary winding of the transformer; and in which means are provided toderive a substantially sine wave output signal from the secondary'of thetransformer.

2. The combination set forth in claim 1 in which means are provided toderive a substantially rectangular output signal wave from the other ofthe cathodes of the gas tube.

3. In a multi-stage cascaded frequency divider, in which each stagecomprises a gas tube circuit responsive to alternate pulses suppliedthereto, and in which there is included in each stage a non-gaseouselectron discharge device for supplying pulses to the gaseous alternatepulse responsive means, the non-gaseous electron discharge device forthe first stage being connected to an external source of pulses, thenon-gaseous electron discharge device for the subsequent stages beingconnected to receive, sharpen, and amplify pulse signals derived fromthe gas tube of the preceding stage to amplify the latter, andconnections from the non-gaseous device to supply controlling pulses tothe gaseous tube of the following stage, whereby the output of eachgaseous alternate pulse responsive circuit is amplified to provide apulse of sufiicient amplitude reliably to trigger the followingalternate pulse responsive gaseous tube circuit.

References Cited in the file of this patent UNITED STATES PATENTS2,415,654 Place Feb. l1, 1947 2,593,375 Williams et al Apr. 15, 19522,780,751 Ridler Feb. 5, 1957

